TP-235

Accumulating evidence suggests that NLRP3-mediated alveolar macrophage (AM) pyroptosis and subsequent high mobility group box protein 1 (HMGB1) secretion play significant roles in the pathogenesis of acute respiratory distress syndrome (ARDS). Nrf2 has been shown to be individually involved in regulating pyroptosis. In this study, we investigate the ability of CDDO-imidazolide, a potent Nrf2 activator, to regulate AM pyroptosis and HMGB1 secretion in sepsis-associated ARDS, along with its underlying mechanism. The in vitro alveolar macrophage (AM) pyroptosis model, established by stimulating J774A.1 cells with LPS and ATP, was treated with CDDO-imidazolide or utilized Nrf2-knockout cells. The mice are intraperitoneally administered with CDDO-imidazolide before the in vivo sepsis-associated ARDS model is constructed via caecal ligation perforation and the Nrf2 inhibitor, ML385. In vitro studies reveal that the use of 3-MA to prohibit PINK1/Parkin-dependent mitophagy aggravates NLRP3-mediated pyroptosis and HMGB1 release in J774A.1 cells via LPS and ATP exposure. CDDO-imidazolide also significantly prevents NLRP3-mediated pyroptosis and HMGB1 release to increase PINK1/Parkin-dependent mitophagy, but these effects are not detected in Nrf2-knockout macrophages. Most importantly, CDDO-imidazolide significantly alleviates NLRP3 inflammasome protein expression in the lung tissues of septic mice and HMGB1 protein levels in the serum and bronchoalveolar lavage fluid (BALF), which can be reversed by ML385. Taken together, our results demonstrate that CDDO-imidazolide prominently protects the lungs by promoting Nrf2 activation and enhancing PINK1/Parkin mitophagy to inhibit AM pyroptosis and HMGB1 release. These findings provide novel insights for therapeutic strategies for sepsis-associated ARDS.

WT and Nrf2-deficient mice were treated with inflammatory stimuli and CDDO-Im prior to transfusion with RBCs expressing the KEL antigen (KEL+ RBCs). Anti-KEL IgM and IgG were measured in the serum of transfused mice. Nrf2-activated gene expression and interferon activity were measured in mice and human macrophages pre-treated with CDDO-Im and interferon stimuli.

Here, we report that CDDO-Im induces Nrf2-activated gene expression and inhibits type 1 interferon activity, which promotes RBC alloimmunization in transfusion models. In mice transfused with KEL+ RBCs, pre-treatment with CDDO-Im inhibited inflammation-induced anti-KEL antibody production and increased the post-transfusion recovery of KEL+ RBCs in a Nrf2-dependent manner. CDDO-Im also inhibited RBC alloimmunization in mice with pre-existing inflammation.

These results indicate that the activation of the Nrf2 antioxidant pathway regulates RBC alloimmunization to the KEL antigen in a pre-clinical model. If these findings translate to other models and human studies, Nrf2 activators may represent a potential prophylactic intervention to inhibit alloimmunization.